Rapid action electrolytic cell

ABSTRACT

An electro-refining cell having a series succession of alternating anodic and cathodic frames through which an electrolyte is circulated at a relatively rapid rate, the anodic frames containing current-distributing electrode rods of impure metal and fragmented impure metal. Insulating and sealing means space the frames apart and create a static zone beneath the frames and the main flow path so that anodic slimes settle out of the electrolyte through screens forming the bottoms of the anodic frames. The slimes are removed periodically from the static zone by dragging or by flushing the zone with a flow of electrolyte.

Jan. 2, 1973 w. A. HUBBARD RAPID ACTION ELECTROLYTIC cm.

Filed May 24, 1971 United States Patent O1 ice 3,708,415 Patented Jan. 2., 1973 3,708,415 RAPID ACTION ELECTROLYTIC CELL Walter A. Hubbard, deceased, by Ruby C. Hubbard, legal ig grfientative, P.O. Drawer 399, Carrizozo, N. Mex. Continuation-impart of application Ser. No. 725,383, Apr. 30, 1968. This application May 24, 1971, Ser. No. 146,280

Int. Cl. C22d 1/02; C231) 5/70; B01k 3/04 US. Cl. 204-257 16 Claims ABSTRACT OF THE DISCLOSURE An electro-refining cell having a series succession of alternating anodic and cathodic frames through which an electrolyte is circulated at a relatively rapid rate, the anodic frames containing current-distributing electrode rods of impure metal and fragmented impure metal. Insulating and sealing means space the frames apart and create a static zone beneath the frames and the main flow path so that anodic slimes settle out of the electrolyte through screens forming the bottoms of the anodic frames. The slimes are removed periodically from the static zone by dragging or by flushing the zone with a flow of electrolyte.

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of co-pending application Ser. No. 725,383, filed Apr. 30, 1968, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the electro-refining of metals, and has particular reference to an electrolytic cell in which a soluble anode of crude metal is decomposed in its electrolyte under the influence of an electric current, and is deposited as pure metal on a cathode spaced from the anode in the enriched electrolyte.

For example, copper ore is smelted to produce impure copper metal, known as blister copper, containing several metallic and non-metallic impurities, and the blister copper is cast into heavy electrodes which are suspended as an anode in the cell, in spaced relation with a cathode which may be a starting sheet of the pure metal. The elec trolyte, which may be copper sulfate, is circulated past the anode of impure copper to receive copper ions therefrom, and then past the cathode where the ions are deposited as pure copper on the starting material. For high production purposes, the electrolyte is passed through a series of alternating anodes and cathodes.

As each anode is dissolved, the impurities in the metal are released into the electrolyte as so-called slimes, which are allowed to settle out and separate from the electrolyte. While it has been recognized that high rates of flow of electrolyte through such a cell are important to good electrolysis and control of the deposition of a pure metal at the cathode when the electrolyte becomes dilute, such high flow rates prevent the settling out of slimes from the electrolyte, causing their possible loss and contamination of the otherwise pure metal being deposited at the cathode.

Moreover, it also has been recognized that close spacing of anodes and cathodes is important to the creation of a strong electrolytic field and low electrical resistance, so as to obtain greater deposition in a single pass of the solution. In practice, however, it has been deemed necessary to maintain relatively large gaps to avoid shortcircuiting of the cell by contact between the electrodes as a result of buckling under the currents used.

Finally, conventional electro-refining techniques and apparatus have the disadvantage of lost efliciency resulting from down-time for replacement of anodic material, removal and replacement of completed cathodes, and removal of built-up anodic slimes.

SUMMARY OF THE INVENTION The present invention resides in an improved method and apparatus for the rapid and continuous electro-refining of metals such as copper in which the electrolyte may be circulated at relatively rapid rates without interfering with the separation of anodic slimes, and in which the anodes and cathodes may be suspended in closely spaced, side-by-side relation with relatively narrow and closely controlled gaps without danger of shorting out.

More specifically, and as illustrated in the preferred embodiment shown and described herein, the invention resides in an electrolytic cell having a generally horizontal series succession of alternating anodic and cathodic zones, with means for confining the flow of electrolyte to a generally horizontal channel while producing a static zone in the lower portion of the cell for the settling out of slimes. For these purposes, the anodic and cathodic zones are defined by frames having porous insulating coverings and suspended in closely spaced relation in the cell, and seals between the frames block off the lower portion of the cell from the main flow path. The anodic frames have open lower ends with screens for supporting the impure metal therein while permitting slimes to settle through chambers in the lower end portions of the frames for periodic removal through the static zone and a trough therein.

In addition to separating the static zone from the main flow channel, the seals maintain the frames in properly spaced relation and cooperate with the insulating covers in preventing shorting out of the electrodes. For easy insertion and removal of the frames, and quick electrical coupling and uncoupling, longitudinal bus bars are provided along the sides of the channel for both the anodes and the cathodes, which have transverse bus bars with coupling elements engageable with the longitudinal bus bars to suspend the frames in preselected positions in the channel. Electrode rods extend downwardly from the transverse anodic bus bars to distribute the electric current throughout the anodic frame.

Other objects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of an electrolytic cell embodying the novel features of the present invention, parts of the cell being broken away to show the interior of the cell and the anodic and cathodic frames therein;

FIG. 2 is a fragmentary plan view of the cell with longitudinal portions and some of the frames removed for compactness and clarity;

FIG. 3 is an enlarged partial plan view of a cathodic frame;

FIG. 4 is a side elevational view of a cathodic frame in the scale of FIG. 1, parts of the central portion and the porous covering being broken away;

FIG. 5 is an enlarged fragmentary plan view of a transverse bus bar for one of the anodic frames;

FIG. 6 is a fragmentary side elevation of an electrode rod for an anodic frame;

FIG. 7 is a side elevation of an anodic frame, also with a central portion and other parts broken away; and

FIG. 8 is an enlarged fragmentary plan view of the anodic frame of FIG. 7 with parts removed to show the screen therein.

3 DETAILED DESCRIPTION As shown in the drawings for purposes of illustration, the invention is embodied in an electrolytic cell, indicated generally by the reference number 10, into which an electrolyte 11 is delivered through an inlet manifold 12 (FIG. 2) and a riser chamber 13 to flow generally horizontally from left to right through a series succession of alternating anodic and cathodic frames 14 and 15, respectively, to an outlet riser chamber 17 having an overflow spillway 18 and an outlet through a fitting 19. During such flow, the electrolyte 11 is enriched through electrolysis with ions of the metal to be refined from impure metal in the anodic frames 14, and ions of the pure metal are deposited on the cathodic frames for eventual removal and use.

The body of the cell 10 is an open-topped tank which may be supported on legs 20 and made of conventional cell material such as concrete lined throughout the chemically inert, electrically insulative material such as Bakelite, backed by asphaltum. As shown in FIGS. 1 and 2, the tank has parallel longitudinal sidewalls 21, a bottom wall 22, a right end wall 23, and a left end wall 24 having an opening 25 communicating with the interior of the riser chamber 13, which preferably is formed in a box-like extension 26 of the tank constructed of the same materials as the body of the cell.

One or more upright longitudinal partitions (not shown) may be placed in the cell 10 to divide it into a plurality of parallel flow channels each having alternating anodic and cathodic frames. The single channel shown herein, however, is sufficient to illustrate the principles of the invention as they are applied to both single channel and multiple channel cells.

The anodic and cathodic frames 14 and 15 are vertically elongated, hollow structures shown most clearly in FIGS. 4 and 7, and are suspended in the cell 10 in alternating, side-by-side relation as shown in FIGS. 1 and 2. For this purpose, a longitudinal shoulder 27 is formed along each sidewall 21 0f the tank, below the upper edge 28 of the sidewall, and each electrode frame 14, 15 has laterally projecting lugs 29, 30 (see FIGS. 4 and 7) which overlie the shoulders 27. In the case of the cathodic frames 15 (FIG. 4), the lugs 30 are under the laterally projecting opposite end portions of a transverse bus bar 31 held on top of the cathodic frame by pins 32 (FIG. 4), and are composed of conducting material to complete an electrical circuit through longitudinal cathodic bus bars 33 set into the insulating material on the shoulders 27. Preferably, the lugs 30 are wedge-shaped in cross-section and fit into correspondingly shaped, longitudinally spaced pairs of aligned notches 34 in the cathodic bus bars 33 to position the cathodic frames 15 precisely in the cell 10.

In the case of the anodic frames 14 (FIG. 7), the lugs 29 are pinned at 35 to the upper end of the frame to project outwardly on each side, and to rest on the cathodic bus bars 33. These lugs, however, are merely supports, and thus are composed of insulating material, the anodic circuit elements of each of these frames being a transverse bus bar 37 which projects laterally on each side of the frame above the supporting lugs 29 with wedge-shaped lugs 38 under each end portion, and with spaced, elongated electrode rods 39 depending from the transverse bus bar into the interior of the anodic frame, As shown in FIGS. 1 and 2, longitudinal anodic bus bars 40 are set on the insulating material along the upper edges 28 of the sidewalls 21 of the tank, and formed with spaced pairs of wedge-shaped locating notches 41 alternating longitudinally with the cathode notches 34 to receive the lugs 38 and thereby position the anodic frames 14 between the cathodic frames 15. Electrical terminals 42 and 43 (FIG. 1) are connected to the bus bars 33 and 40, respectively, for connection to external power lines of appropriate polarity.

With particular reference to FIGS. 3 and 4, it will be seen that each of the cathodic frames 15 comprises a pair of upright, parallel end plates 44, to the top of which a transverse bus bar 33 is secured, and a bottom wall 45 extending between the lower ends of the end plates and closing the lower end of the frame. The sides of the frames are porous, and herein comprise perforated side plates 46 and an optional porous sheet 47 which covers each side plate. The end plates, bottom wall, side plates and cover sheets are composed of insulating material.

Inside each cathodic frame 15 is an open framework or skeleton structure supporting the pure starting metal upon which the refined metal is to be deposited. The starting metal is shown in FIGS. 3 and 4 as a large number of short cylindrical tubes 48, although it will be evident to those skilled in the art that a wide variety of shapes may be used to present a large surface area to the electrolyte for the depositing of metal. The entire interior framework in the cathodic frame is composed of the pure starting metal so that it may be removed as a unit from the cathodic frame after the framework has been filled with deposited metal. With this arrangement, the cathodic frames may be left in place in the cell whenever the interior frameworks are removed and replaced.

Each of the anodic frames 14 is formed by a pair of spaced end plates 49 (FIG. 8) and two perforated, insulating side plates 50. Porous cover sheets 51, of material such as glass cloth, line the side plates to cover the perforations 52 therein, and preferably are bonded to the side plates. The tops of these frames are open to permit the addition of impure, anodic material in fragmented form at any time during processing, and to admit the electrode rods 49 into the frames. These rods also may be composed of impure anodic material so as to be decomposed along with the fragmented material. For ease of replacement, they hang downwardly through holes 56 (FIG. 5) in the transverse bus bar 37 of the frame, preferably having tapered heads 53 which seat tightly but removably in corresponding tapers defining the holes 52.

An important feature of the invention is the manner in which anodic slimes are separated from the electrolyte in the cell 10 while permitting a rapid rate of flow of the electrolyte through the cell. For these purposes, the anodic frames 14 are provided with perforated bottom walls, herein screens 54 (see FIG. 8), through which anodic slimes can settle out of the frames to be trapped in a staticzone 55 below the frames, and transverse seals are provided between adjacent frames near the lower ends thereof to confine the flow of electrolyte to a central flow path above, and separated from, the static zone.

Herein, these seals are formed by elongated sealing strips 57 of insulating material secured to the cover sheets 47 of the cathodic frames 15 across the lower ends thereof, to engage the adjacent sides of the anodic frames 14 as shown in FIG. 1. The sealing strips preferably are of rounded, semi-oval vertical cross-section to facilitate upand-down relative movement of the frames, and have a relatively soft, synthetic rubber coating for a good sealmg action.

It will be seen that these strips 57 not only seal off the static zone 55 from the main flow channel, but also determine the proper spacing of the lower end portions of the frames. Preferably, similar sealing strips 58 are secured to the cover sheets 47 of the cathodic frames 15 adjacent their upper ends, to space and seal between the frames along the upper side of the flow path. In addition, each frame 14, 15 preferably has a vertical sealing rib 59 along each side, and the inner sides of the sidewalls 21 of the tank are formed with vertical grooves 60 (FIG. 2) which receive these ribs to seal the frames between the frames and the sidewalls. It is important to note that the sealing strips 57 and 58 and the porous insulating elements between adjacent frames permit the frames to be arranged in very closely spaced relation while maintaining a sufficient gap between adjacent frames.

The screens 54 near the lower ends of the anodic frames 14, as best shown in FIG. 8, may be braced by one or more cross struts 61 so as to be able to sustain the weight of the fragmented anodic material in the frame. As indicated in FIGS. 1 and 7, each screen is spaced above the lower end of the frame and below the perforations 52, near the effective sealing level of the strips 57, so that the slimes released by dissolving anodic material are effectively separated from circulating electrolyte and trapped in the static zone 55 beneath each anodic frame. The sealing strips 57 and the bottom walls 45 of the cathodic frames isolate the interiors of these frames from the static zone.

To facilitate removal of accumulated slimes from the static zone 55, the bottom wall 22 of the tank is dished transversely of the flow path, and may be formed with a longitudinal trough 62 as indicated in FIG. 1. The bottom wall and the trough also slope downwardly to some extent from left to right, the direction of flow of the electrolyte. Thus, accumulated slimes may be flushed from the static zone 55 through the trough and an outlet door 63 at the right end of the static zone, using a forced flow or jet of electrolyte from an inlet 64 at the left end of the static zone, or by dragging the slimes to the right through the static zone and out through the discharge door, the cathodic frames 15 being raised slightly for this.

Alternatively, a drain 65 is provided near the lower, right-hand end of the trough 62 with a valve 67 that may be opened briefly to draw out slimes. Opening of this valve creates a momentary flushing flow of electrolyte from the main flow path downwardly through the anodic frames 14 and along the trough to the drain, and effectively clears out most of the slimes without any down-time for the cell.

Although the manner of operation of the cell should be apparent from the foregoing, a brief summary of the operation will emphasize more clearly the novel features of the present invention. Assuming that the metal to be refined is blister copper, the electrode rods 39 are cast of this material and the remainder of the space within the anodic frames 14 is filled with fragmented blister copper. The removable frameworks with the cathodic frames are composed of pure copper starting material, as are the cylinders 48 in the cathodic frames.

With such frames 14 and 15 suspended from the longitudinal bus bars 33 and 40, in alternating relation as shown in FIG. 1, and with appropriate electrical connections to the terminals 42 and 43, the electrolyte 11 is introduced into the riser chamber 13 through the manifold 12 to fill the cell, trapping a quantity of air in the sealed upper end portion 68 of the riser chamber to maintain an input pressure on the electrolyte, controlled by a relief valve 69 (FIG. 1).

The electrolyte thus is forced from the riser chamber 13 through the opening 25 in the front wall 24 of the tank and into the first anodic frame 14 through the perforations 52 and the porous sheet 51. Seals 70 above and below the opening confine the input flow to the central portion of the frame. In passing through the first frame, the electrolyte is enriched with copper ions released from the blister copper therein, and, as an incident to the dissolving of the blister copper, insoluble anodic slime materials are released into the electrolyte.

As the enriched electrolyte flows on through the downstream sidewall of the anodic frame 14 and into the first cathodic frame 15 through its porous cover sheet 47, the released slimes are trapped in the anodic frame and settle downwardly therein, through the screen 54 and into the static zone 55, and thus are separated from the main flow of electrolyte, which flows around the starting metal in the cathodic frame to deposit ions of copper thereon under the influence of the electric current.

This process repeats as the electrolyte flows through each pair of frames 14, 15 toward the right end of the cell 10, where the electrolyte enters the riser chamber 17 and exits through either the outlet fitting 19 or the spillway 18. Of course, anodic slimes are released in each anodic frame, and collect in the static zone 55 beneath these frames.

After a selected period of operation, the accumulated slimes may be removed from the static zone 55, either by shutting down the cell, raising the cathodic frames 15, and dragging or flushing the slimes through the door 63, or by flushing the slimes out of the static zone through the trough 62 and the drain 65 without interrupting the electrolysis. With any of the alternatives, the slimes are effectively trapped and removed to prevent loss thereof with the electrolyte and contamination of the deposits in the cathodic frames.

As the blister copper is consumed, the fragmented material may be replenished through the open upper ends of the frames 14, and the rods 39 may be replaced by prying the upper ends out of the holes 56 in the transverse bus bars 37, and inserting new rods in their places. Similarly, as the framework within a cathode frame 15 becomes filled with deposited copper, it may simply be lifted out of the frame and replaced with a new frame work.

Although the description has been directed specifically to the electro-refining of copper, the same approach is applicable to other impure metals which may be used as soluble electrodes in solutions of their electrolytes, as will be readily apparent to those skilled in the art. Whether the metal is copper or some other metal, the present invention permits substantially higher rates of circulation of the electrolyte without danger of loss of slimes or objecionable contamination of the deposited metal, while at the same time controlling the gaps between closely spaced electrode frames to avoid shorting out of the frames.

It will be apparent that, while a particular embodiment and arrangement of process steps have been illustrated and described, various modifications and changes may be made without departing from the spirit and scope of the invention.

I claim:

1. An electrolytic cell for the electrorefining of impure metal by dissolving the metal in an electrolyte and depositing the metal electrolytically, said cell having:

a tank for holding the electrolyte;

means for creating a flow of electrolyte along a selected I path through said tank;

a series of alternating anodic and cathodic frames arranged along said path in spaced, side-by-side relation;

said frames having porous sidewalls for passing the electrolyte successively through the frames to dissolve impure metal in said anodic frames and deposit the metal electrolytically in said cathodic frames;

said anodic frames having means forming perforated bottom walls for the settling out of insoluble anodic materials from within the anodic frames;

and means adjacent the lower ends of said frames confining the fiow of said electrolyte to above said lower ends and creating a static zone in said tank beneath said frames for the accumulation of settled out slimes.

2. An electrolytic cell as defined in claim 1, in which the last-mentioned means comprise transverse sealing strips between adjacent frames near the lower ends thereof, each of said sealing strips being mounted on one of the frames and abutting against the other both to confine the flow to above said static flow and to space the frames a preselected distance apart.

3. An electrolytic cell as defined in claim 2, in which a second set of transverse sealing strips is disposed between the upper end portions of the frames.

4. An electrolytic cell as defined in claim 2, further including sealing means between said frames and the sidewalls of said tank.

5. An electrolytic cell as defined in claim 4, in which said sealing means between said frames and the sidewalls of said tank comprise elongated ribs slidably fitting in elongated grooves.

6. An electrolytic cell as defined in claim 1, in which said means forming perforated bottom walls are screens.

7. An electrolytic cell as defined in claim 1, in which said frames are hollow, box-like structures suspended in said cell in closely spaced relation, said cathodic frames having closed bottom walls, and said anodic frames having sidewalls formed with perforations covered by porous sheets.

8. An electrolytic cell as defined in claim 7, in which said flow-confining means are transverse sealing strips on the lower ends of said cathodic frames pressed against the adjacent sides of said anodic frames, and further including similar strips adjacent the upper ends of said cathodic frames.

9. An electrolytic cell as defined in claim 7, in which said frames are suspended in said tank by means including laterally projecting lugs on opposite sides of each frame, and upwardly facing shoulders extending along the sides of said tank and engaging said lugs.

10. An electrolytic cell as defined in claim 9, in which the lugs on at least one type of said frames are on transverse conducting bars mounted on the upper end of the frames, and further including longitudinal conducting bars on said shoulders engaging the lugs to complete an electrical circuit therethrough.

11. An electrolytic cell as defined in claim 10, in which said transverse conducting bars are mounted on said cathodic frames, said anodic frames having insulating supporting lugs engaging said conducting bars, and further including additional transverse bars extending across the upper ends of said anodic frames, additional longitudinal conducting bars on said tank engaging said additional transverse bars, and soluble electrode rods spaced apart along each additional transverse bar and depending into the associated frame to distribute current therein.

12. An electrolytic cell as defined in claim 7, in which said cathodic frames are composed of insulating material, and have open frameworks of the pure metal removably supported therein.

13. An electrolytic cell as defined in claim 1, in which said tank has a bottom wall forming a trough extending along said path beneath said frames in said static zone.

14. An electrolytic cell as defined in claim 13, including means for flushing slirnes out of said trough independently of the fiow of electrolyte along said path.

15. A11 electrolytic cell as defined in claim 14, in which said flushing means include an inlet for electrolyte adjacent one end of the trough and an outlet adjacent the other end thereof.

16. An electrolytic cell as defined in claim 13, in which said flushing means include a drain from said trough operable when opened to produce a downflow of electrolyte through said anodic frames and said trough to said drain.

References Cited UNITED STATES PATENTS 1,517,631 12/1924 Jones 204-287 1,517,630 12/1924 Jones 204-287 1,407,313 2/1922 Allen 204-259 1,011,459 12/1911 Mackay 204-257 835,329 11/1906 Snodgrass 204-257 569,722 10/1896 Morrow 204-287 1,074,274 9/1913 Mackay 204-257 JOHN H. MACK, Primary Examiner R. L. ANDREWS, Assistans Examiner 

